Your cat should still be okay to go outside. However, she will be less agile, and more succeptable to coyotes and other preditors, not to mention cars. If you want her to have her kittens in your house, then it might be advisable to keep her in (otherwise the neighbours tool she may become her queening pen) Outside itself won't hurt her or her kittens as long as you are deworming and defleaing regularly. I would make sure she is in at night so that she can eat the food that you have for her, we don't want her to go hungry. (make sure you are feeding a high quality kitten food - lots of healthy calories for Mum and babies!) If she insists on going out, keep an eye on her, or keep her on a leash. She probably would be just as happy inside as out - many cats are! Hope this helps
Cheers
Kim